The LTPS technology has been used more and more widely due to its advantages such as ultra thinness, a low weight and low power consumption.
A planarization layer is provided in a structure of a LTPS backboard. The planarization layer is made of a relatively thick organic material. Therefore, during a process of forming the planarization layer, a great amount of exposure generally is needed to completely remove organic materials that require being removed for avoiding the residues. However, the great amount of exposure will cause a deflection of a threshold voltage of a thin film transistor (TFT).
In summary, the ultraviolet light used when the planarization layer is exposed adversely affects properties of the TFT so that the stability of the TFT is reduced.